Compound cylinder



Patented Sept. 24, 1935 UNITED STATES PATENT OFFICE COMPOUND CYLINDERHerbert 0. Bowen, Detroit, Mich., assignor to Hydraulic Brake Company,Detroit, Mich., a corporation of California Application April 22, 1932,Serial No. 606,784

12 Claims.

power.

An object of my invention is to provide a compound cylinder wherein theoutlet port is connected directly to the large cylinder.

Another object is to provide a compound cylinder wherein no fluid isby-passed back to the reservoir when the low pressure piston becomesinactive.

Another object is to provide a new and improved compound cylinder.

Other objects and advantages will become apparent as the descriptionproceeds.

In the drawings, Fig. 1 is a vertical section of one embodiment of myinvention;

Fig. 2 is a similar view of a second embodiment of my invention;

Fig. 3 is a view of the embodiment illustrated in Fig. 1 but shows theparts in the positions they assume when the low pressure cylinderbecomes inoperative; and

Fig. 4 is a view of the embodiment illustrated in Fig. 2 but shows theparts in the positions they assume when the low pressure cylinderbecomes inoperative.

Referring to Figs. 1 and 3, I have illustrated my invention as having acasting .5 providing a high pressure cylinder 6 and a low pressurecylinder I. The casting also provides the base 8 of a reservoir 9 havinga wall ID of sheet metal or other suitable material. The wall I0 isclamped between a gasket ll carried by the base 8 and a spider I2 whichis fastened by means of screws It to a flange l3 formed by the upper endof the casting 5. The edge l5 of spider I2 oyerhangs the wall Ill andserves as a retaining means for the rubber boot I6 which covers theupper end of the reservoir.

A piston I1 is located in the high pressure cylinder 6 and is moved influid discharging direction by a piston rod l8 which may be actuated bya foot pedal, hand lever, or any other suitable ma ually-operated orpower-driven mechanism. The lower end of the piston rod I8 is roundedand simply rests in a socket formed in the upper end of the'piston Hwith which the lower end of the piston rod l8 forms a separableconnection.

A low pressure piston I9 is threadedly secured to the. high pressurepiston i1 and the joint between the two is sealed by a rubber gasket 20which also forms a seal between the high pressure piston and the wall ofthe high pressure cylinder. A

port 21 connects the reservoir with the high pressure cylinder when thehigh pressure piston is in the retracted position shown in the drawings.When the parts are in the position shown in Fig. 1 of the drawings, thelowpressure cylinder 1 5 is also in communication with the reservoir byway of port 2| formed in the wall of the high pressure cylinder, highpressure cylinder 6, diagonal passageways 22 cutting across a comerformed at the junction of two different diameter por- 10' tions of thelow pressure piston, annular space 23 formed between the wall of the lowpressure cylinder and the reduced portion of the low pressure pistonimmediately in rear of the head thereof, passageway 24 formed in thewall of the low 15 pressure cylinder immediately in rear of the head ofthe low pressure piston, passageway 25 provided by a boss integral withthe wall of the low pressure cylinder, and passageway 26 formed in thewall of the low pressure cylinder at a point 20 immediately in front ofthe sealing cup associated with the head of the low pressure piston.

The low pressure piston l9 has a cylindrical chamber 21 in which islocated a relief valve spring 28 acting on a piston 29 provided with a25 sealing gasket 30 and a forward extension "3| which functions as avalve to close the opening in an annular washer 32 mounted .in theforward end of the low pressure piston.

A rubber cup 33 forms a seal with the wall of 30 1 cylinder I and alsoprevents leakage between the extension 3| and washer 32.- The cup 33 isheld against the forward or lower face of the low pressure piston byretractile spring 34 which has one of its ends abutting against a sheetmetal cup 35 35 and its other end resting against a sheet metal valvebody 36 which is pressed against a gasket 31 clamped between the end ofthe casting 5 and a shoulder provided by a cap 38 which is threadedlysecured to the lower end of the casting.

The valve body 36 has out-let ports 33 which are normally closed by theflange of a rubber cup 40. This valve mechanism is described and claimedin United States Letters Patent No. 1,985,936, of January 1, 1935, inthe name of 4 Erwin F. Loweke.

One or more fluid conduits 4! may beconnected to the cap 38. Theseconduits may lead to brake operating cylinders of the type disclosed inUnited States Letters Patent No. 1,832,135, of '50 November 1'7, 1931,or to any other mechanism operated by fluid pressure.

' With the parts at rest as shown in Fig. 1 of the drawings, the spring34 holds the high and low pressure pistons in their elevated orretracted 66 positions. Both the high and low pressure cylinders are infree communication with the fluid reservoir. The upper part of thecylindrical chamber 21 is in communication with the reser- 'voir 9 byway of passage 42 formed in the low pressure piston, andradial passages43 formed in the high pressure piston and which lead to longitudinalgrooves 44 likewise formed in.the high pressure piston. The power end ofthis chamber 21 is also in communication with the reservoir by way ofport 45, annular space 23, passageways 22, high pressure cylinder 6, and

When force is exertedupon the piston rod IS, the high and low pressurepistons move downwardly, closing the ports 26 and 2|, respectively, andcutting off communication between the reservoir and the high and lowpressure cylinders. After the low pressure piston has passed the port26, continued downward movement of this piston forces fluid from the lowpressure cylinder through the ports 39 and thence to the conduits 4|. Asthe low pressure piston moves downwardly, the annular space23 increasesin length, and the fluid necessary to fill the increased capacity ofthis annular chamber is drawn from the reservoir through grooves 44 andpast rubber gasket 20, the outer edge of which collapses sufliciently topermit this flow of fluid 'therepast.

When the pressure in the low pressure cylinder and conduits reaches apredetermined value, the force exerted on the end of extension 3| issufficient to overcome spring 28, whereupon piston 29, gasket 30 andextension 3| move upwardly relativeto the low pressure pistonand thelower end of extension 3| is withdrawn from the opening in the washer 32as shown in Fig. 3. This establishes free communication between thefront and rear sides of the low pressure piston by way of the centralopenings in cup washer 33, washer 32, and port 45.

Rearward movement of the piston 29 is limited by the engagement of theupper end of its rearward extension46 with the shoulder 41. Thereafterthe fluid can by-pass the low pressure piston and this piston becomesinoperative. The burden of creating additional pressure is. then assumedby the high pressure piston which continues to advance, thereby forcingadditional fluid into the conduits 4|.

When the desired braking effect has been accomplished, the operatorrelieves the force exerted on the piston rod l8, whereupon this rod maybe returned to initial position independently of the pistons by means ofthe retractile spring commonly associated with the brake lever or by anyother suitable means where my compound cylinder is used in fluid systemsother than those associated with hydraulic brakes. The high and lowpressure pistons are thereupon returned to their retracted position bythe spring 34.

In hydraulic brake systems it frequently hap-' pens that the piston ofthe compression cylinder is returned faster than the pistons of thebrake actuating cylinders so that a sub-atmospheric pressure is createdin the compression cylinder. In my compound cylinder the creation ofsuch a sub-atmospheric pressure would result in drawing fluid from thereservoir through ducts 44 and past rubber gasket 20 into the high,pressure cylinder 6.

shown in Fig. 1 of the drawings, thereby closing As soon as the pressurein the low' pressure cylinder dropped, due to the withdrawal of forcefrom the piston rod l8, the extension 3| would be returned by spring 28to the position pressure cylinder 5|, low pressure cylinder 52,

high pressure piston 53 and low pressure piston 54. The pistons arereciprocated on their fluid discharging stroke by piston rod I8, as inthe previous embodiment.

In this embodiment the high pressure piston 53 is held in elevatedpositionby a spring 55 which rests on the low pressure piston 54. The

latter piston is held in elevated or retracted position by a spring 56which is somewhat strongerthan the spring 55.

In the position of the parts shown in Fig. 2, the high pressure cylinder5| is in free communication with the reservoir by way of opening 51formed in the rubber cup 58, passageways 60 and 6|, and grooves 62. Ifdesired, a, port 63 may also be provided. The low pressure cylinder 52communicates with the high pressure cylinder 5| by means of passageway64 formed in the piston 54 and rubber and metal cups 65 and 66.

Initial downward movement of the high pressure piston closes the port 63and brings the rubber cup 58 into engagement with the base 61 of acylindrical member 68, thereby cutting off communication between thehigh pressure cylinder and reservoir 58. Further advance of the highpressure piston causes corresponding advancement of the cylindricalmember 68, thereby compressing relatively weak spring 69 until the lowerend of this cylindrical member engages shoulder 10, whereupon furtheradvance of the high pressure piston creates equal advance of the lowpressure piston.

By the time the lower end of cylindrical member 68 has engaged shoulder18, valve H has entered passageway 64 and sealed against rubber cup 65,thereby closing the opening through the low pressure piston. Furtheradvance of the high and low pressure pistons causes the low pressurepiston to discharge fluid into conduits 4| through ports 39 formed invalve member 36. As the low pressure piston advances, it creates avacuum in back of it which draws additional fluid from the reservoirthrough grooves 62 and past the collapsed edge of rubber cup 58.

When a predetermined pressure is reached, valve H is moved rearwardlyagainst the tension of spring 12, thereby establishing a. by-passthrough the low pressure cylinder by way of passageway 64, the interiorof cylindrical member 68, and port 13 as shown in Fig. 4. Thereafter thefluid may freely by-pass the low pressure piston and the high pressurepiston functions as the sole means for creating pressure on the fluid inconduits 4|.

During the retractile stroke of the pistons,

additional fluid from the reservoir may be sucked into the high and lowpressure cylinders by means of grooves 62 and passageways 14.

While I have illustrated and described two embodiments of my invention,it is to be understood that my invention may assume numerous forms andthat the scope of my invention is to be limited solely by the followingclaims.

I claim:

1. In a hydraulic system of the class described, the combination of aconduit, a low pressure cylinder connected to said conduit for supplyingfluid thereto, a high pressure cylinder discharging into said lowpressure cylinder and communicating with said conduit only through saidlow pressure cylinder, pistons in said cylinders, a valved connectionbetween said cylinders, and means for operating said pistons.

2. In a hydraulic system of the class described, the combination of aconduit, a low pressure cylinder discharging into said conduit, a highpres- .sure cylinder communicating with said conduit only by way of saidlow pressure cylinder, a valved connection between said cylindersadapted to open when the low pressure cylinder attains a predeterminedpressure, pistons in said cylinders, and means for reciprocating saidpistons.

33. In a fluid system of the class described, the combination of aconduit, a cylinder communicating with said conduit, a piston forcreating a relatively low pressure therein, a second piston for creatinga higher pressure in said cylinder, a

valve for automatically rendering said firstnamed piston inoperativeupon the creation of a predetermined pressure in said cylinder wherebysaid high pressure is communicated therethrough to the conduit, andmeans for reciprocating said pistons.

4. In mechanism of the class described, the combination of a largecylinder, a piston reciprocable therein, said cylinder having a fluidoutlet, a fluid reservoirfor said cylinder, a smaller cylinderinterposed between said reservoir and said large cylinder, said largecylinder communicating with said reservoir through said small cylinder,pistons in said cylinders, and means for operating said pistons.

5. In mechanism of the class described, the combination of a fluidreservoir, a high pressure cylinder communicating therewith, a lowpressure cylinder communicating with said high pressure cylinder andsupplied with fluid therefrom. a conduit connected to said low pressurecylinder, a piston in each of said cylinders, a loaded valve in said lowpressure piston, said valve openable to permit fluid to flow from infront of the sealing portion of said piston to the rear thereof, andmeans for operating said pistons.

6. In a fluid system of the class described, the combination of alignedhigh and low pressure cylinders, a fluid reservoir communicating with:said high pressure cylinder, a piston in each of said cylinders, saidpistons being rigidly connected, a fluid receiving conduit connectedsolely with said low pressure cylinder, means for operating saidpistons, and means for connecting the low pressure cylinder with saidhigh pressure cylinder upon the creation of a predetermined pressure insaid low pressure cylinder.

'7. In a compound cylinder of the class described, the combination of alow pressure cylinder, a high pressure cylinder, pistons in saidcylinders, a fluid reservoir, means establishing communication betweensaid cylinders and said reservoir when said pistons are in retractedposition, means for advancing said pistons, and means operative upon thecreation of a predetermined maximum pressure in said low pressurecylinder to open a passageway through the low pressure 5 piston andestablish communication between the parts of said cylinders on thepressure sides of said pistons.

8. In mechanism of the class described, the combination of a lowpressure cylinder, a fluid 10 reservoir, a high pressure cylinderlocated between said low pressure cylinder and reservoir andestablishing communication therebetween, a piston in said high pressurecylinder, a piston in said low pressure cylinder for discharging fluidtherefrom and for simultaneously drawing additional fluid from thereservoir and into said high pressure cylinder in front of the high.pressure piston therein, and a conduit for receiving the discharge fromsaid cylinders.

9. In mechanism of the class described, the

combination of a low pressure cylinder, a fluid.

reservoir" therefor, a high pressure cylinder providing communicationbetween said cylinder and reservoir, pistons reciprocably mounted insaid 25 cylinders, means establishing communication between saidcylinders when said pistons are in retracted position, means foradvancing said pistons to out 01f communication by way of saidlast-named means, and other means to reestab- 30 lish communicationbetween said cylinders upon the creation of a predetermined pressure inone of saidcylinders. v

10. In a compound cylinder of the class described, the combination of alow pressure cyl- 35 inder, a high pressure cylinder, a piston in eachof said cylinders, the low pressure piston having a port therethroughfor establishing communication between those parts of said cylinderswhich are in advance of said pistons, a loaded valve 40 controlling saidport, means for reciprocating said pistons, a fluid reservoircommunicating with said high pressure cylinder, and a discharge conduitconnected to said low pressure cylinder.

11. In mechanism of the class described, the 45 combination of a highpressure cylinder, a low pressure cylinder, a high pressure piston inthe high pressure cylinder, a low pressure piston in the low pressurecylinder, said last-named piston having an opening therethrough, a valveoper- 50 ated by the initial protractile movement of said high pressurepiston to close said opening, operating means for said pistons, and. aconduit receiving the discharge from said cylinders.

12. In a hydraulic system of the class described, the combination of aconduit, a low pressure cylinder connected to said conduit for supplyingfluid thereto, a high pressure cylinder discharging into said lowpressure cylinder and communicating with said conduit only through said60 low pressure cylinder, pistons in said cylinders, a valve subject tooutside pressure and the pressure in the low pressure cylindercontrolling communication between said cylinders, and means foroperating said pistons. A

HERBERT C. BOWEN.

